Screening of Lactic-Acid Bacteria from South African Barley Beer for the Production of Bacteriocin-like Compounds

Strains ofLactobacillus paracasei subsp.paracasei (strain ST11BR),L. pentosus (strain ST151BR),L. plantarum (strain ST13BR), andLactococcus lactis subsp.lactis (strain ST34BR) producing bacteriocin-like peptides were isolated from barley beer produced in the Western, Northern and Eastern provinces of South Africa. The peptides (bacST11BR, bacST151BR, bacST13BR and bacST34BR) lost their activity after treatment with proteinase K, a proteinase, papain, chymotrypsin, trypsin, pepsin and pronase, but not when they were treated with α-amylase, suggesting that the peptides are not glycosylated. The peptides inhibited the growth ofLactobacillus casei, L. sakei, Pseudomonas aeruginosa, Escherichia coli andEnterococcus faecalis, but notEnterobacter cloacae, Lactobacillus bulgaricus subsp.delbrueckii, L. plantarum, L. salivarius, Listeria innocua, Staphylococcus aureus, Streptococcus uberis, S. agalactiae, S. caprinus andS. pneumoniae. Peptides bacST11BR and bacST13BR differed from the other 2 peptides by failing to killKlebsiella pneumoniae and one of theE. coli strains. Peptides were stable after 2 h of incubation at pH 2.0–12.0, and after 90 min at 100 °C. When autoclaved (121 °C, 20 min), only bacST13BR lost its activity. The bacteriocin-like peptides were produced at a growth temperature of 30 °C, but not at 37 °C.